1 files changed, 14 insertions, 0 deletions
diff --git a/gcc/fwprop.cc b/gcc/fwprop.cc
index 4ee44ad..59df7ca 100644
--- a/gcc/fwprop.cc
+++ b/gcc/fwprop.cc
@@ -836,6 +836,20 @@ forward_propagate_into (use_info *use, bool reg_prop_only = false)
   if (def_insn->is_artificial ())
     return false;
 
+  /* Do not propagate asms.  The only kind of propagation that would
+     succeed is propagation into a register move.  Such a propagation
+     is neutral if the destination of the move is a pseudo and unnecessarily
+     restricts the register allocator if the destination of the move is
+     a hard register.
+
+     Furthermore, unlike for a normal instruction, we cannot take a SET from an
+     asm and try dropping the CLOBBERs.  The recog process does not (and should
+     not try to) second-guess whether what the user wrote can be changed and
+     so it has to assume that any asm given to it is a fair reflection of
+     what the user wrote.  */
+  if (def_insn->is_asm ())
+    return false;
+
   rtx_insn *def_rtl = def_insn->rtl ();
   if (!NONJUMP_INSN_P (def_rtl))
     return false;